People with accents from a foreign country are generally perceived as less knowledgeable, credible, and trustworthy than those who share one’s native tongue. And those with a familiar regional accent are perceived as more confident and approachable. Accents shape how a speaker is perceived, and in today’s culturally diverse work environment this perception, although subjective, can have a detrimental effect. 

"People have an inherent evolutionary bias of favoring members of their own group and accent is one way we can quickly decide if someone is different ", says Marc Pell, director of the School of communication Sciences and Disorders at McGill University. Pell and his colleagues recently explored the accent bias and concluded that participants perceived the accented speakers as less believable – unless they had an especially confident tone.
                 
Displaying confidence may be an effective way to offset the prejudice prompted by an accent.

Source: Phycology Today | March/April 2019